Color management refers to the process of processing color-related data so that colors are represented consistently across a variety of different devices and media. Color management systems can use color measurement devices to obtain representations of the color of a given surface.
The human visual system processes color within the visible portion of the electromagnetic spectrum in terms of the red, green, and blue components of this spectrum. This characteristic of the human visual system has led to the development of color management systems that measure, represent, and process colors using a three-channel approach for performance optimization reasons. In this approach, separate channels are devoted to measuring, representing, and processing the short, middle and long wavelength components of a given spectrum or achromatic, and orthogonal color difference channels.
Another approach to measuring, representing, and processing colors involves capturing a spectral representation of a given color. Such a spectral representation divides a portion of the electromagnetic spectrum (for example, the visible portion of the spectrum) into a number of channels corresponding to particular wavelengths or frequencies of interest. The spectral representation of the given color indicates how much energy or power that the components of the given color project into the wavelengths or frequencies of interest.
Diffraction gratings may be used to split an input beam of light into its spectral components. Typically, these components correspond to the wavelength or frequency components that combine to constitute the input light. In this sense, diffraction gratings produce results that are somewhat similar to those of a prism. If a diffraction grating is used in connection with a three-channel color management system, the red, green, and blue components of the input light may be collected and processed or alternative three channel representations can be collected and processed as appropriate such as CIEXYZ, CIELAB or YCC. If the diffraction grating is used in connection with a color management system that processes spectral representations of colors, then the diffraction grating may be adapted to generate three or more of the components of the input light. In any event, diffraction gratings typically present the chosen components of the input light simultaneously, rather than one-at-a-time or sequentially.
Because typical diffraction gratings produce their output components simultaneously, color measurement devices that operate with such typical diffraction gratings generally include a plurality of sensors or detectors. For convenience and conciseness, the term “sensor” as used herein is understood to refer to both a sensor and a detector. In a three-channel color management system, one sensor is typically dedicated to each one of the three channels. Thus, three sensors are provided, with one sensor for each of the red, green, and blue channels.
In a color management system processing spectral representations of colors, the output bandwidth of the diffraction grating may be divided into a one or more of wavelengths or frequencies (i.e., channels) of interest. The number of such channels depends on the resolution or granularity desired in the color management system, and this number may exceed three depending upon the capabilities of the post processing capabilities of the system. In any event, such spectral systems typically provide one sensor for each channel, a relationship similar to the three-channel systems discussed previously.
Whether in the context of a three-channel system or a system using spectral representations, typical color measurement devices typically employ one sensor for each channel or color component of interest. This one-to-one relationship between the sensors and the channels can increase the cost, bulk, and complexity of color management devices. Also, more particularly in the spectral context, if it is desired to analyze input light with more resolution and granularity, more channels are added. However, with these additional channels typically come additional sensors. Adding more sensors means that the same number of photons is shared among more sensors, thereby depleting the photon well available to each sensor and possibly causing an undesirable signal-to-noise (S/N) ratio for each sensor. Therefore, designers of color measurement devices and/or color management system that perform spectral processing may be faced with a trade-off between enhancing the resolution of the system, or having a system with a favorable S/N ratio.
Finally, some diffraction gratings may be manufactured from expensive optical materials, such as achromatic glass. Such diffraction gratings may be customized into specific cross-sections or configurations as appropriate to isolate specific frequencies or wavelengths of input light for analysis. All of the foregoing characteristics of typical diffraction gratings can increase the cost and bulk of a color management device that is manufactured using such typical diffraction gratings.